Continuous method and apparatus for calcining and clinkering



R. D. PIKE Y CONTINUOUS METHOD AND APPARATUS FOR CALCINING AND CLINKERING Filed'Dem l, 1 920 5 Sheets-Sheet 1.

IN V EN TOR WITNESS ATTORNEYS Oct. 20, 1925- v 1,557,873

R. D. PIKE CONTINUOUS METHOD AND APPARATUS FOR CALGINING AND CLINKERING Filed Dec. 1, 1920 s'sheets-sheet' 2 IN VEN TOR ATTORNEYS Oct. 20, 1925. 557,873

R. D. PIKE CONTINUOUS METHOD AND APPARATUS FOR CALCINING AND CLINKI JRING Filed Deg. 1; lo 5 Sheets-Sheet 5 WITNESS h IN V EN TOR I V fl, 30mg z/ WW 0%:

' ATTORNEYS Oct- 20,192s- 1 5 7,873

' R. D. PIKE CONTINUOUS METHOD AND APPARATUS FOR CALGINING AND CLINKERING Filed Dec. 1, 1920 5 Sheets-Sheet 4 mwllllll'i l I I 11v VENTOR A TTORNE YS Oct. 20,1925. 11557.873

R. D. PIKE CONTINUOUS METHOD AND APPARATUS FOR CALCINING AND CLINKERING Filed Dec. 1, 1920 5 Sheets-She et 5 IN VEN TOR i VITNESS 0% J M BYQ.5-Qwfr M aw m I ATTORNEYS ever, the rotary into the stack kiln briquets of proper size Patented 0a,, 20, 1925.

' oon'rmuous v To all whom Be it known that citizen of the United States, Francisco, in the county 5 I and State of California,

tain new and useful tinuous Methods and Apparatus for cining and Clinkering,

in is a specification.

nonna'r-n. rnmi or SAN rnanorsco; c-anrronnm.

itmay concern:

I, ROBERT D. PIKE, a residing at San of San Francisco have invented cer- Improvements in Con- Calof which the followhe hereinafter described invention re-' 'l'ates to an improved method and apparatus for the conducting and carrying out of a continuous process for the calcination of substances composed largely rocks, such as calcite and magnesite,

of carbonate and the ,forming of the calcined product by chemical combination at high temperature Into a'clinkered or semi-fusedmass.

It will be and clinkering. of the understood that the calcination products composing Portland cement and dead burned magnesite fall within the scope of the present invention, the object of the invention being to accomplish the calcination and clinkering of the material use of fuel,

with greater economy in "the to increase the output of the clinkeredmass from a single unit of given capacity, and to improve product.

the quality of .the

l At present there is utilized in the art for the calcining two well known types known as the stack kiln and the other ing and clinkering of such material of machines, one beas the rotary kiln. It has'been long known that dead burned magnesite and cement clinker can be produced in stack kilns with materially less fuel In the former,

top thereof, becoming calcined duced at the and converted intov the raw material is introclinker, passing 'down,

and finally being drawn from the bottom in a substantially cold condition. Howkiln has supplanted the stack kiln by reason of certain advantages which serve as an volved in its the material offset 'to the high fuel cost inuse. For example, the feed of into the rotary kiln is in a pulverulent form, while the feed of the material of the draft must be in lumps or to permit the passage upward through the kiln, and

at the same timemust be strong enough to hold up the quirement o burden of the charge.

Thls ref the stack kiln introduces a than used in rotary kilns. "heat, but the temperature a great waste of mz'rrronanp APPARATUS son cancmme AND ounxnmnof Application filed December 1, 1920. Serial ml 427,4ea-

great difficulty when two or more raw mate, rials have to be intimately mixed to produce a clinker of the desired composition, because the separate materials are required first to be formed into lumps or bri uets after being ground and mixed, and t ese lumps or briquets in most cases are not'strong enough to support the burden of the charge without crumbling while passing through the stack kiln. The rotary kiln overcomes this difficulty in a perfectly obvious manner by taking the materials in a pulverized form and keeping the particles in a state of agitation and in intimate contact, one with the the process of calcination other, throughout and clinkering. The rotary kiln produces a clinker of substantially uniform quality, while the clinker from the stack kiln always has to 'be selected to remove the under burned material, and the rotary kiln has-a much larger capacity than the stack kiln and employs less labor per ton of material produced. v

In the rotary kiln the material enters at the upper or more elevated end, due to'the rotation of the kiln, passes downwardly. All of the the flame, The gases of combustion passing upwardly from the clinkering zone, effect calcinationof the downwardly moving material before (it enters the clmkering zone.

The formation of clinker from the calcined material is an .operation re'quiring but little heat and in some cases actually liberating required is high; while the calcination is an operation absorbing much heat at'a temperature considerably below that required for clinkering. It results, from the operation in the rota I V I fuel is injected at and is burned a at or near the lower end, and the formation of clinker is effected inthe hottest part of kiln in which the dissimilar reactions of ca cining and clinkering are carried on under similar conditions, that the calcina'tion is not performed efiicientlyQ An excess, amount of fuel is invariably injected to cause clinkering, over that required to effect calcination, provided the latter operation were performed ciently. The resultjs that there is always I heat energy up the'stack from rotary kilns, tially' recovered in present use of waste heat boilers.

and in rapid succession,

which can only be parpmactice by the f as In the stack kiln, the same conditions pres vail in a general way, but the operation is slower and" a eater surface of the material being calcine 'is exposed to the hot gases 'leav1ng the clinkering zone. This results in the hot gases giving up more oftheir heat in' performing the operation of calcination, and in their passing upthe stack at a lower temperature than is possible in thero- 1 tary kiln. o t With the present invention the fuel economy of the stack kiln is bettered, and at the same time greater capacities are attained than are now possible yvith the rotary kiln, as well as better quallty of clinker, while the disadvantage or loss of either form of afiiparatus is eliminated, thereby permitting t e carrying out of a continuous process of calcina'tion and clinkering at a 'niaterially 2 less cost than that at which the same has heretofore been accomplished.

In general, the method consists in first subjecting the raw pulverulent material to the action of a flowing stream of air and gases of combustion to effect, the. heating thereof, and subsequently treating thejmate rial while passing downwardly in countercurrent to the said stream of air and gases of combustion to produce calci 9 nation; thence without allowing the'calcined m aterial to come into contact with the out side atmosphere, transferring the same from y the calcining means to clmkermg means,

and causing the calcined material to move through the clinkering means while in contact with a counter flowing stream of airand gases of combustion heated to a tempergture sufiicient to produce clinkering of. the calcined material, and conveying the waste products'of heat from the vclinkering means to the calcining means, to serve asa portion of the heat units for calcination; thence. without allowing the clinkered material to come into contact with 5 phere, transferring the same from the'clin'k- \ering means to a cooling means and subjectmg the material therein to a counter flowing stream of air which absorbs, the

heat therefrom and conveys it to the clinkering means, thence afterwards to the calcining means where it assists in the respective operations. In other words the treatment of the material .isdivided into distinct and separate steps, the first being that of calcination, the second that of clinkering, and the third that of cooling, each step-being carriedout in an apparatus de signed for its most efficient performance.

cAn efficient apparatus for carrying out the method'invention comprises the use of a furnace for calcining,of the circular multiple-hearth type, with rotating-radial rabble arms, an associated rotary furnace for clinkering, and a rotary cooler for receiving 96 the clinkered material from the rotary kiln.

travelling hot cining furnace, for these gases from the rotary furnace are rich. 1n oxygen and-contaln the outside atmos- 'furnace by any one of several calcining furnace or directly into the latter,

one or more of the hearths of thefcalcining thongs-through the ,cooler. The air and gases of combustion and calcination pass in continuous counter-current to the material,

entering the lower end of the cooler and leaving'the top of the calcining furnace'in a relatiyely cool condition, In the clinkeringfurnace the stream of highly heated air from the -cooler is continuously augmented by the addition 9f just suflicient fuel to effect clinkering, and in the calcining furnace the stream of highly heated air and... gases of combustion and calcination is continuously augmented by the addition of just suificient fuel to effect calcinatiomand the upper part of the calciningfurnace the heat of the gases is given up in heating 4 the materials to the calcining temperature. There. is thus established a continuous counter-current of material in a downwardly direction and of gases and air in an upwardly direction, passing successively through separate apparatus, each piece of apparatus being highly efiicie'nt for the purpose for which it is intended, and each util-x izingthe waste heat from' all of the appa- .ratus beneath it.

In carrying out the method by the said apparatus, all of the hot gases from the ro-' tary kiln passdirectly to the calciningfurnace, entering the latter over the. lower hearth or lower several hearths. Here they" assist directly in calcination due to the'heat I j they contain, and indirectly by furnishing the oxygen to burn the fuel firedin the cala sufiicient quantity of it to burn all" ofthe fuel'required for calcination. v j -I The additional fuel required for calcinathe calcining means. Coke braize or any kind of finely divided coke may be mixed with the materials before treatment. This coke is I ignited byv the hot gases'from the rotary furnace eitherv alone or assisted by. auxiliary burners Which may inject fuel either into; the flue connecting the rotary kiln with the tion may be introduced into and in burning furnishes the'heat necessary forv calcination. Coal in a'more or less finely subdivided condition-for. :example, ground to pass 8-mesh-n'1ay be fed on to furnace by any suitable means, either downthrough the central rotating shaft of the furnace or through openings in the furnace shell. verized coal or gas into t-hecalcinlng furnace or into the path of the hot gases from the Suitable burners may inject 'oil, pulrotary rotary ikiln; Any desired combination of the mentioned means of firing the calcining furnace may be used.

The rotary clinkering furnace is fired by" To comprehend the method inventionand a form of apparatus for carryin out the same, reference should be had to t e accompanying sheets of drawings, wherein Figure 1 is a side elevation of -the-a paratus, said view illustrating the vertica mule tiple-hearth element wherein the calcinatio'n of the material is accom lished as fed therethrough, a longitudina ly' disposed rotaryclinkering member connected to the vertical member by means of a closed conduit, also disclosing the bypass connection between the vertical element and the rotary elem'ent whereby the waste products of heatescaping from the rotary element are conveyed to thev vertical element, also'di'sclosing the rotary cooler associated with the clinkerlng member of the -apparatus, throu h which the clinkered material "is passed for cooling, and the bS'Pi connection between the rotary cooling element and I v the rotary clinkering element whereb the on line Y-Y Fi Figure 7 is a ongitudinal sectional view.

heated air from the former, is trans eln ed to the latter. Figure 2 is a vertical sectional view of the vertical multiple-hearth calcining element of the apparatus. I

Figure 3 is a longitudinal sectional view taken through the rotary cooler, rotary clinkering elements of the apparatus, and through the connection between the vertical alcinmg element and the rotary clinkering element of the apparatus.

Figure 4 is a vertical sectional view taken on line XX of Figure 1 and viewed in.

the direction of the arrows.

Figure 5 is a longitudinal sectional view through a protected rabble arm and the central rotating column of the vertical calcinin furnace. x

igure 6 is a cross sectional view taken re 5 of the drawings.

through one of the un rotected rabble arms. .Figure 8 is a bro en vertical sectional viw of means for feeding coal on to hearths in the vertical calcining furnace.

In the drawings, the numeral 1 is used to designate the vertical element of the apparatus employed for calcination, 2 designates 'not in operation.

through a closed dischar inside the dust chamber is the hot air by the fire clay tlles 13 and the being approximately 6 feet in diameter by all the heat from the hot clinkers intermix- 30 the rotary element of the apparatus utilized for the clinkering vof the material tr'ansferred thereto from the vertical element 1,

and 3. designates a rotary cooler situated in a plane below that of the rotary element 2, which is designed to receive the hot clinkered material from the said element. The rotary element 2 utilized in the present apparatus is of a. length of approximately 50 feet more or vle'ss'and of a diameter of approximately 8 feet, and is provided with a v tapered upper end 5. The said rotary kiln 2 is lined throughout interiorly with refractory. brick lining 6 and is provided at its lower end with a firing hood 7 through which is introduced a burner 8; The said hood 7 does not rot-ate with the element 2, but surrounds the lower end of said element and is mounted'on wheels 9 so as to permit of the'same beingmovedtoward or from 1 the kiln 2 in an axial direction, to provide v accessto the interior of the said kiln when The running joint between the firing hood and the kiln 2 is made as tight as possible t'o'reduce the, leak- 9 age of air to a minimum and the said firing hood 7 is provided with a protected sight hole 10 and is further'provided with a discharge opening 11 in the bottom thereof, which permits of the hot clinkers discharging from the rotary kiln 2.to drop or pass e spout 112, water cooled where exposed to t e hot air, into the Y upperend of the rotary downwardly inclined cooler 3. The n pered end of said coo er 3 enters into, a chamber 13 through" a rotating seal I 14, which seal is adapted to prevent the leakage of outside air into the system. {The chamber 13 is preferably formedof sheet metal, lined onthe inside with fire brick backed. by insulating brick. up The seal 14: be-

tween the tapered end of therota'ry cooler '3 and the chamberv 13 is similar in all rethe rotary kiln 2 and the vertical kiln 1.

The exposed surface of the "rotary cooler rotected from annular ring 13 for cooling. The 'rota cooler 3v in constructiony is similar to t at of the rotary member 2,.

approximately 90 feet in length, and its function. is to receive heat from the hot clinkers discharged through the spout 12 v and transfer this heat into the. air for com-V bustion, which heated air passes on upwardly into the rotary kiln 2 through the' bypass connection 17, thereby reducing loss from radiation to a' minimum and insuring ing with the air passing through the cooler P r duced o m0 from its lower end, which is open "to the atmosphere.

The'interior upper 45 feet more or of the rotary cooler is lined'with refractorybrick of dense, hard composition backed up by insulating brick. As the clinker passes from this portion of the cooler into the upper end of the lower 45 feet more or less, it

is barely red hot. In the lower 45 feet more or less the clinker is in contact with the inside of the rotating steel shell which is air, This lower length of the cooler is provided with lifting vanes 24 which drop the clinker througlrthe upwardly passing lined-on the outside with insulating mate'- rial', the Qiid cooler permitting the transferring of practically all of thev heat from the clinker to 'theair' for-combustion which,

. is very when it leaves the upper end of the cooler,

metal surfaces exposed to it.-

The exposed surface of the rotary kiln 2 inside the dust ,cha'mberlfi is protected from heat by fireclay.tiles 18 and an annular ring 19- for cooling. The dust chamber .16 is provided with clean-out doorsw20 for the dust:-chamber.16 and the lower portion ofthe calcining furnace 1. ,Clean-out doors 4 are provided tomake easy the removal of discharge" spout 23, through which spout. the vcalcined material discharging from, the furnace 1' flows downwardly-and is .intro-. ducedinto the upper tapered end fift s removing of accumulated dust, and-the inner walls of said chamberJare ,lined with refractory brick backed .up by insulating material. The said dust chamber is connected with the lower portion of the vertical calcining furnace 1 by means of the bifurcated fine 21, said fluepreferably being made of sheet metalflined with suitable refractory and :insulating material, andthe same is connected by tight joints 22 with the said dust from the inside surface. The' said calcining furnace 1 is connected with. the

rotaryikiln 2 by means of a water-cooled rotary kiln 2. I

-' The, construction .of the calcining furnace 1- is disclosed as to details in Figures 2, 5, 6 and 7. of the drawings.

. material in pulverulent form to be calcined is delivered into the upper end portion of the said furnace,t he

' gases from the said furnaceescapin'g therefurnace within which the material from through the conduit 25. The vertical 1s calcined is preferably com osed of an outer steel shell 26, suitab y supported or upheld by" the supports 27 and the shell 26 is provided with .the. inside refractory lining "wall 28 separated from hot, necessitating protecting all The "prepared furnace -.1 in any suiti able manner, preferably. through the medium of the feed box. 24,-which. is adapted tocontinuously feed-the raw material lnto the the metallic shell 26 by means of. the insulatinglinin'g'29. Within the cylindrical furnace 1 isarranged aseries of hearths 30 and 3h. which hearths' are arranged in superposed relation. The said hearths are of circular form" and are projected inwardly from theflining 28, the series of 'hearths '30 being provided with a central aperture 'to provide a clearance 32 for the free passage of material between the inner peripheral Wall thereof and the central air cooledre volving column 33, while" the hearths 31 are provided, adjacent the lining 28, each with a-series of cutouts. oropenings 34,

through which material under treatment esing upwardly through the furnace, the cooler.

portion of the furnace or that portion from A upwardly having the saidcentral air cooled 1 hollowshaft unprotected by refractory lining.

The' central has rotation imparted thereto by any suit-' stance by the gear- 39 which meshes with a drive gear 40 driven from any suitable source of outside power. This hollow cen- .tral shaft is composed essentiallyof two hollowshaft 33 is'driven or 95 able form "of drive mechanism, as for inpartsean inner-cylinder '33 and an outer cylinder 33 the latter enclosingwithin itself the formerand an annular space 34. 'Air for cooling is introduced into the lower extremity of the inner cylinder (a suitable running joi nt, being provided-to prevent leakage of airto the outside' atmosphere.) and passes-radially outwardthrough a number-of passages 39 whichconducts it shaft are rigidly attached a "series of air through" the-annular space 34 and delivers. .it outside'of'the central shaft. Tothe' said .Qool'ed unprotected rabble arms 41 and pro comprises within itself: two longitudinal passages 42- fand. 42 connect-ed at their outer extremityj with-each other. 'One of inner end 'withone 'of the passages "39", connecting with the I interior cylinder 'of the tected arms 42, Each of these rabble arms these passages of each arm registers at iff central rotating shaft, and the other regi's-1 ters wi th. a passage 39? connecting with the annular space .34; The latter isconnected at its upper end' with a stationary air pasresult, of this arrangement is that cold air under pressure enters the lower extremity of thecentral cylinder of the hollow rotating sage 40-through a running joint 40. The 2 I nucaevs' shaft, and passes outwardly through one .lon 'tudinal passage. of each rabble arm,

. and is thence discharged from the upper part of the furnace.

Each of the protected rabble arms 42 .is provided on its sides with the longitudinally disposed feathers '40 and on its bottom with the longitudinally disposed V-shaped recess 40 The fire clay U-shaped tiles 40 are adapted to slide over the said rabble arm engaging with the feathers 40 and butting at the inner. end of the rabble arm again t the fire clay tiles 44'. Y

When fitted over the rabble arm 42, the said U -shaped tiles 40 are held in locked position by means of 'the end lock tile 44 which is 'attached to the projecting end 44 of the rabble arm 42 by means of the secure ing bolts 44.

The rabble arms/11 in the portion of the furnace above A aremade in the -usual fashion of cast iron, and do not have to be protected, but the rabble arms '42 in the part of thefurnace below A have to be protected from theexcessive heat of calcinetion to prevent injury and also to prevent the excessive loss of heat to the circulating air. It is tobe understood that in this apparatus such heat as passes to the circulating air is practically all wasted, for this air cannot be utilized for combustion, it, being necessary for. highest efficiency tobring all the air for combustionin the calcining furnace up through the cooler and clinkering furnace. I p I The rabble arms 41 and 42 are provldedrespectively with the rabble teeth a and bk 1 which are above the v hearths 31 the angle of the rabble teethis so v ,move the material inwardly. a are of the usual design and are made of cast iron, but rabble teeth, 6 are made of disposed projection 41.

disposed as to move the material outwardly, while on the alternate rabble arms the angle of the rabble teethis so disposed as to Rabble teeth nickel .chrome alloy or some other all? ormetalresistant to high temperature; an are so made as to permit of a refractory lining 44. being interposed between theirxu per side and the bottom of the protectedra ble arms.

The rabble teeth I) of the protected rabble. arms are formed integral with atop plate a 41, whlch plate is vprovglded or formed with tended wedge shaped central longitudinally This we ge shaped projection-is adapted to slide within the V'- sha ed recess 40, and serves to secureftliek pos1ti0n of the teeth in'proper relation to the material being treated.

To prevent material and gases passingbe tween those of the hearths over which the material moves outwardly, and the central rotating column or shaft, the seals 44. and 44 are provided, the former being made of cast iron and the latter of nickel chrome alloy or any alloy or metal resistant-to the action of high temperature.

Figures5 and]; how detail of construction of a protected rabble arm, and the pro- I tected' central rotating shaft.

The bifurcated flue 21 from the dust chamber 16 introduces the hot airand-gases from the rotary clinkering furnace through the several ports 43 over the lower three hea'rths of the calcining furnace. The gases '-'leav1ng the up er hearth of the calcining furnace prefer-a 1 pass through a suitable .lower three hearths. These burners may use either pulverized coal, gas or oil for fuel and may or may not be used continuously, but in anyevent are provided as auxiliary means for heatingthe calcining furnace.-

F gure 8 discloses means for .firin -.-the calcining furnace, where coal is 'emp 0 ed precipitator 414, w ich removes the (1ust,, 4

The

as thecombustible medium. Coal groun so of that all will pass 8-mesh screen is the preferable fuel used. This is fed onto the fifth hearth from the bottom, on; which hearth the material is moving outwardly.

The coal is fed by an automa'tic feeder, ada ted to maintain any desired feed,:into

the; opper 50, and passes downwardl into the vertically disposed'cylinderol.

e lat- 'ter terminates the u' per endlof a feedpi e 52, the center of w ich coincides-withe I axisof the rotating central shaft. The lower end of thepipe 52 terminates in the two branches '53 and 53','sloping downwardly' ata sharp angleand passing through both the. wall of the inner and outer c linder of the .central rotating shaft." The ower ends of the branches are flattened to'have a rectangulart opening with long) axis in a horizontal plane. Immediately of the branches are rectangular openings 54, connectin with the interior of the inner cylinder of t e central rotating shaft; The refractory removed, leavin a more or less square-opening; 56, which'gives a free passage from the passages 54 and the ends of t e branches 53 and 53 into the calcinin furnace. outer cylinder" of the centra elow the lower ends no r protection v35 of the latter, immej the side flanges 41". and the upwardly ex-idiately'in frontof the extremities of the; branches b3 and 53, and-the-passages5 4,'is-

The r rotating shaft connects through the runnin joint 40 with the bent pipe 40", which con note the heated the centralshaft, extends through the pi e conical part 61.- The conicalplunger 62-is 40 and thrppgh' the stuflingbox 60. T e cylinder 51 is connected to the pipe-52 by a adapted to find a seaton the inside surface of the conical part 61. This plunger does not rotate, but its position u and down may be altered by turning the and Wheel 62" which engages the screw 63and the stationary support 64. The smooth shankof the screw 63 is .furtlger sup'p'orted by the spider and bearing 65 v 4 y In operation, the automatic feeder is set to deliver uniformly the desired amount of coal, andthe height of'the conical plunger. 62 is so regulated, that the cylinder 61 remains full of coal, thus preventing cold air being drawn into the. furnace down the feed pipe 52. The falling coal isv equally d1- vided between the branches 53 and 53" of the feed pipe, and as-itemergestfrom their lower ends is blown by the air issuing under pressurethrough the opening 56 in a fanshape curtain out over the material on the furnace hearth, thus givin a uniform feed o f cpalwith a small quantity. of air. .Hav-

ing once been uniformly deposited on the hearth, the coal is uniformly moved forward by the rabble teeth. .The air issuing through the openings 56 also serves to keep the coal in the nozzle below the carbonizing point.

. -When thecoal is deposited over the'ma- -terial on the hearth, its volatile constituents immediately ignite and burn, until the com-.

' bustible gases are entirely consumed.v The nonvolatile or coky'constituents of the coal In the pass downwardfy with the material to beca-leined, and their combustible matter i entirely consumed before the materalleaves the calcining furnace; The coal can be just.

as easily'spread over additional.hearths, al-. 1

thou h one will usually suflice.

'divided coke as a fuelin the calcining-furnace, no special apparatus is needed, itbeing simply necessary to mirthe'coke with "the speak the bottom of the vertical furnace, is provided witha discharge port 64, through which the calcinedmateria discharges into the w.atercooled closed chute or 'spout 23. for delivering the same into the, rotary kiln or furnace 2. Y

. means for carrying out the method invention, the material to be treated in pulverized.

form is. fed in. a continuous stream by any;-

kiln, thence passing downwardl ed in proper proportionbeforefin- 7 .troduction into the top of the calcining operation of the above described hearth from the bottom) of thecalcining furnace. Thence it passes downwardly 1n zig-zag course over'thesuccessive hearths. In the upper portion of the furnace heat s imparted to it by the gases of combustion an calcination passing in counter-current to rotary kiln eifectswcalcination in the lower five hearths. In the manufacture of Portland cement, care must be exercised not'to overheat the material in the calcining furnace, lest incipient clinkering start, which would lie u'ndesirable. In the makingof Portland cement, the temperature of the calcining furnace should not exceed approximately 2000 F., and this temperature may be attained more or less uniformly. on the 'five lower hehrt'hs. In the making of magnesite, a lower temperature, about 160 0 F. is maintained on the lower five hearths; The hot calcined material is dis charged fromthe lowest hearth through the water cooled spout, directly into the rotary eratur'e of the material is rapidly raised y the combustion of theffuel, and the the temclinker begins to form. in the upper portion of the kiln. This clinker. bein jected to the action of heat for its ormation for the comparatlvely long time required to pass to the lower end of the rotary kiln, has all the necessary chemical actions within .itself {thorou/ hly .and uniformly completed, and will ,t erefore be of better and more uniform grade. than the rapidly lformed clinker of the rotary kiln or the im-.

perfect-1y formed clinker of the stack kiln. The temperature of clinkering-in the rotary kiln will range, from 2700 to 3000 o M W with both Portland cement and ma esite.. If 1t 1s desired to use coke bralze or finely kiln and 'thetr'otary coo or are revolved means, as or instance by the. gear ring 65 thereon meshing with the driven gear 66:

When the clinker leaves the lower end of the rotary kiln it still retains almost the maximum temperature, and all that is necrotary cooler. The clinker is discharged Considering the'operation of the firing of x tion.

essa'ry is that the'heat be extracted in thethe a paratus, cold atmospheric -.jair is in duce to enter the lower open .end of the rotary cooler bythe draft withinthe apparatus, andleavlng the upper end enters the rotary kiln in a'highly heated state; The

draft inthe apparatusis regulated either by. the speedo the exhausting fan or by-aj damper in'the stack, if thelatter is used. The operator regulates the quantity of fuel fed into the rotary kiln, so that just enough is used to complete the operation, of which he can judge by the appearance of the clinker which he can observe through suitu ably arranged sight-holes which are covered with Pyrex glass to prevent the infiltration of cold air. The amount of coal to be fed into the calcining furnace is arbitrarily chosen and is kept in constant ratio to the feed by suitably arran ed automatic feeders of any well known esign. From 70 to 85% of the total fuel required is fed to the calcining furnace. This quantity will vary with the material being treated, and with the judgment of the operator.

The net result of the operation of this method and apparatus is that both the clinker and the stack gases are discharged at relatively cool temperatures, which is an indication of its high fuel economy, and the clinker is of exceptionally uniform and high quality;

A further understanding of the reason for the great capacity and high fuel economy inherent in this method and apparatus may be had by considering the area of material exposed in the inside of the apparatus to the hot gases, as related to the outside area of the apparatus exposed to the atmosphere, and comparing this relation to the same relation in the case of a rotary kiln. Take for example, with the new method and apparatus, a rotary kiln 8 in diameter by 50' long in combination with a 9-hearth calcining furnace 21 6" outside diameter: The surface of the charge exposed to the action of the gases inside the apparatus is approximately 3,0(20 sq. ft. and the outside area of the apparatus exposed to the atmosphere is approximately 4,600 sq. ft., giving a ratio of outside surface toinside surface of 1.54. A rotary kiln 10 in diameter would have to be about 600 long to have the same area of charge exposed inside the apparatus (it is mechanically impractical to make a rotary kiln 600 long, 200' appearing to be the highest practical limit) and the outside area exposed to the atmosphere would be 18,850 sq. ft. giving a ratio of outside to inside area of 6.28.

It therefore follows from this comparisonthat economical units in accordance with this invention can be made in larger size than when using a rotary kiln, and the ratio of radiation losses to useful work performed will necessarily bemuch smaller than with the rotary kiln. The losses by radiation may further be made smaller in the new apparatus than in the rotary kiln, because the stationary shell of the calcining furnace can be more thoroughly insulated than can the rotating shell of the rotary kiln. i

By the use of my invention I am able to effect a saving in the manufacture of Portland cement of from to cents per barrel, and in dead burned magnesite of approximately $2.00 per ton, as compared with any known method of manufacture. ;The

saving efi'ected will depend of course in great measure upon the price of fuel. In

addition, I am enabled to build practicalcommercial units of greater capacity than is possible by present known means, thus effecting a saving in charges for handling material.

Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is as fol-' lows 1. The continuous method of calcining contact with a counter-flowing stream of heated air and gases having a temperature sufliciently higher than that required for calcination, to cause clinkering of the said material, and passing the waste products of heat from the said rotary structure into the first mentioned structure for the utilization thereof as a portion ofthe heat for calcination- 2. An apparatus for the described pur pose, the same comprising a vertically dis- ,verulent form, then while contained within a posed stationary calcining furnace, means therein for propelling pulverulent material, to be treated therethrough, means for intermixing with the pulverulent material a fuel medium, means for introducing within the furnace a heat medium having a tempera-- ture sufiicient to cause calcination ofthe material passing therethrough and flowing counter-current to the stream of material passing through the said furnace for calcination, arotary clinkering furnace ass0 ciated with the calcining furnace, means for transferring the calcined material discharging from the calcining furnace directly into the rotary clinkering furnace without exosure to the outside atmosphere, means for introducing into the clmkering; furnace a heat medium of a temperature to cause furnace, a cooler associated with the clinker ing furnace and adapted to receive the clinkered material discharging therefrom,

and meansfor delivering air passing through the co oler into the clinkering furnaoe for supporting combustion therein.

3. The continuous method of calcining and clinkering carbonate rock by the action of a flowing stream of heating mediums having different temperatures, which consists in first reducing the material into a pulverulent form, then while contained within a closed stationary structure passing the same counter-current to a stream of heated air and gases to effect the heating thereof, then intermixing fuel therewith, then while contained within the said stationary structure passing the. same through a counter-flowing stream of heated air and gases having sufficient temperature to cause ignition of the fuel and sufficient oxygen to support combustion thereof, toproduce cal- 'cination, then transferring .the same from the said structure to aclosed rotary structure,,and passing the same therethrough in direct contact with a counter flowing stream I of heated air and gases having a temperature sufficiently higher than that required for calcination, to cause clinkering of the said material, and passing the waste products of heat fromthe said rotary structure into the first mentioned structure for the utilization thereof as a portion of the heatfor calcination.

4. An apparatus for the described pur pose, the same comprising a vertically dis posed stationary calcining furnace, means therein for propelling pulverulent material to be treated therethrough, means for intermixing with the pulverulent material a fuel medium, means for introducing within the furnace a heat medium having a temperature suflicient to cause calcination of the material passing therethrough, and flowing counter-current to the stream 'of material passing through the said furnace for calcination, a rotary clinkering furnace associated with the calcining furnace, means for transferring the calcined material discharging from the calcining furnace directly into the rotary clinkering furnace, means for introducing into the clinkering furnace a heat medium of a temperature to cause clinkering of the calcined material as passed there through and counterwise to the flowing stream of the heat -medium, means for conveying the products of combustion from the clinkering furnace into the calcining furnace, a cooler associated with the clinkering furnace and adapted to receive the clinkered material discharging therefrom,vand means for delivering air passing through the cooler into the clinkering furnace for supporting combustion therein.

In testimony whereof I have signed my name to this specification.

- ROBERT D. PIKE. 

